oa Internal Combustion Impulse Source vs. Mini-vibrator vs. Nomad 65 vibrator shot tests

Over the last two decades 3D reflection seismic has been applied for mine planning in South Africa. For coal exploration, the mining targets are at shallower depths of less than 400 m. The challenge set by the mining companies is to obtain high-resolution seismic data with maximum vertical resolution at this depth of investigation. The cost of geophysics must also be more attractive than that of the ‘total drilling’ alternative. Seismic source trials were therefore conducted at one mine site. The ICIS (Internal Combustion Impulse Source) has been developed by CGG to provide a solution for shallow target surveys and for in-fills where access for conventional sources is restricted. The ICIS and Mini-vibrator performance were tested in shallow coal prospects, where existing 2D data have been acquired by Nomad 65 heavy vibrator. The tests demonstrated that ICIS is well suited to image target depths less than 500 m with frequencies up to 100 Hz. The comparison with the vibroseis sources showed that ICIS I) Delivered very good near offset data (> 50 m) and for up-hole/low velocity layer survey ii) Required more shots per shot point in the medium offset range (1000 m) due to its low energy iii) Not designed for far offset data (3000 m). ICIS was found to be a viable geophysical and logistic solution for certain high-resolution mineral surveys.